Method and apparatus for an adaptive multiple-input multiple-output (MIMO) wireless communications systems

ABSTRACT

An adaptive MIMO communications system includes a multifunctional reconfigurable antenna with a selectively alterable effective physical antenna array configuration and radiation/polarization properties, which configuration and properties is a component in the optimization of the adaptive system parameters. The multifunctional reconfigurable antenna comprises a plurality of antenna components and a plurality of selectively controllable switches coupling selected ones of the plurality of antenna components together into a multifunctional reconfigurable subarray of antenna components. A processing unit coupled to the multifunctional reconfigurable antenna determines communication channel conditions for generating adaptive control signals to the plurality of selectively controllable switches to selectively apply a selected space-time coding protocol or a selected beam forming protocol together on the plurality of antenna components depending on channel conditions.

RELATED APPLICATIONS

The present application is related to U.S. Provisional PatentApplication Ser. No. 60/632,111, filed on Nov. 30, 2004, which isincorporated herein by reference and to which priority is claimedpursuant to 35 USC 119.

GOVERNMENT RIGHTS

This invention was supported in part by the Defense Advanced ResearchProjects Agency (DARPA) under grant MDA 972-03-C-0017, the US Air Forceunder grant F04611-03-C-004, and the National Science Foundation (NSF)under grant ECS-0424454. The Government has certain rights to theinvention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to the field of adaptive multiple-inputmultiple-output (MIMO) communications system equipped with multifunctionreconfigurable antennas and adaptive coding schemes.

2. Description of the Prior Art

There has recently been significant research performed on MIMO systemswith associated technologies such as smart antennas and adaptive codingand modulation techniques, which have been proven to dramaticallyincrease the wireless channel capacity and improve the diversity. Makingthe best use of limited and costly wireless bandwidth is the mainmotivation behind these efforts. Although in these studies considerableattention has been given to the performance analysis of these systems inthe context of coding and signal processing architectures, theinvestigation of the antenna aspect is limited to the impact of thenumber of antennas with little consideration of their radiation andpolarization characteristics, and array geometry.

Much has been written in the current literature on MIMO systems, and theassociated transmission algorithms such as space-time codes (STCs) andspatial multiplexing (SM). Spatial multiplexing is a multiplexing schemewhereby different bits are transmitted from different antennae and inindependent communication channels. The common goal of these researchefforts is to make the best use of limited and costly wirelessbandwidths by exploiting high spectral efficiencies offered by multipleantenna systems. Although in these studies considerable attention hasbeen given to the performance analysis of these systems in the contextof coding and signal processing architectures, the investigation of theantenna aspect is mainly limited to the impact of the number of antennaelements with little consideration on their radiation and polarizationcharacteristics as well as array geometry.

The achievable MIMO capacities are highly dependent on the channelmatrix properties, which, in return, are determined by joint and/orseparate roles of all parameters involved. These parameters are thephysical structure of the channel (scattering density and disposition ofthe scatterers), the MIMO algorithms (coding and signal processingschemes), and the antenna array configuration with itsradiation/polarization properties. The mobility and time varying natureof wireless communications increase the interactions among theseparameters and their joint roles become key in realizing theoreticalgains of MIMO systems.

Adaptive MIMO systems that take advantage of varying channel conditionsare of particular interest in this study. In an adaptive system, thesystem parameters are jointly optimized to adapt to the changing channelconditions through link adaptation techniques that can track thetime-varying characteristics of the wireless channel.

The adjustable system parameters recognized in the prior art areidentified as the modulation level, coding rate, andtransmission-signaling schemes such as spatial multiplexing, space-timecoding, and beam forming. The antenna properties of this system arefixed by initial design thereby cannot be changed. In other wordstoday's adaptive MIMO systems are constrained to employ a fixed antennadesign over varying channel conditions.

What is needed is some kind of method and means to maximize theresources available in multiple antenna channels by using optimalschemes at all times.

BRIEF SUMMARY OF THE INVENTION

It is the realization of the invention that there is additional room forfurther exploitation of the theoretical gains of MIMO systems when theantenna/electromagnetic aspects and the associated signal processing andcoding aspects are integrated together in a multidisciplinary approach.The adaptation algorithm must be able to select the best combination ofthe system parameters with respect to the properties of instantaneous oraveraged space-time channel matrix in a continuous way.

In this disclosure, the adaptive process introduces an additional degreeof freedom by treating the antenna array configuration and itsradiation/polarization and frequency properties as an additionalcomponent in the joint optimization of the adaptive system parameters.

We identify interrelationships among transmission-signaling schemes,physical channel conditions, and antenna radiation/polarizationproperties so that the best antenna design for a given transmissionscheme and/or channel condition is always selected. This allows thesystem to approach the theoretical spectral efficiencies offered by aMIMO design. The object of joint optimization of antenna arraycharacteristics and the associated transmission algorithm can only beachieved if each individual element of the array can be dynamicallyreconfigured in its structural geometry, what will be hereinafterreferred to as multifunctional reconfigurable antennas. A reconfigurableantenna alters its radiation/polarization and frequency properties byaltering or morphing its physical structure. The reconfigurable antennaconcept in this study is fundamentally different from the concept ofsmart antennas in the literature.

The object of the illustrated embodiment of the invention is to respond,in a most effective way, to the changes in the propagation environmentwith rapidly changing multipath conditions by enhancing the adaptabilityfeatures of current adaptive MIMO systems, thereby improvingdramatically the performance characteristics of the system.

The fundamental principle of the illustrated embodiment of the inventionis to treat antenna properties (radiation pattern, operating frequency,polarization) and antenna array configuration as additional componentsin the joint optimization of the adaptive system parameters. Since oursystem employs multifunction reconfigurable antennas, the antennaproperties can be dynamically changed and jointly optimized withadaptive transmission signaling schemes such as i.e. beam forming,space-time coding, or spatial multiplexing.

By employing reconfigurable antenna elements as opposed to classicalantenna elements, the selection of the best antenna properties andconfiguration in conjunction with the adapted transmission scheme withrespect to the channel condition becomes possible. This feature improvessystem performance characteristics.

Being able to change antenna properties, i.e. radiation pattern,polarization, operating frequency, enables to shape the characteristicsof the propagation environment for the advantage of the transmissionsignaling schemes so that the best combination of system parameters arealways selected. Conventional MIMO systems are constrained to employfixed antenna properties, which are determined by the initial antennadesign, over the varying channel condition. Thus, non-reconfigurableantenna designs are have none of the above advantages.

The invention has a wide variety of commercial and military uses inwireless communication applications, in particular for use inenvironments with rapidly changing multipath conditions. Multiuserwireless networks such as cellular mobile communication systems (3G,4G), wireless local area networks (Wi-Fi, 802.11a/b/g, WLAN) and manyother applications such as mission-centric and/or individual-centricimplementations of wireless ad-hoc networks, and/or sensor networks aretypical examples of applications. One particular example for commercialuse is the forthcoming very high performance IEEE communicationsstandard, IEEE 802.11n. With our invention the performances of thisstandard can be further improved. The invention will impact the nextgeneration standards, particular in the wireless communications market.

Thus, the illustrated embodiment of the invention can be characterizedas an improvement in an adaptive MIMO communications system comprising amultifunction reconfigurable antenna with a selectively alterableeffective physical antenna array configuration andradiation/polarization properties, which configuration and properties isa component in the optimization of the adaptive system parameters.

The reconfigurable antenna comprises a plurality of antenna componentsof any geometric shape and a plurality of selectively controllableswitches coupling selected ones of the plurality of antenna componentstogether into a reconfigurable subarray of antenna components.

The improvement further comprises a processing unit coupled to thereconfigurable antenna to determine communication channel conditions forgenerating adaptive control signals to the plurality of selectivelycontrollable switches.

The processing unit generates adaptive control signals to the pluralityof selectively controllable switches to apply a selected beam formingprotocol on the plurality of antenna components.

The processing unit generates adaptive control signals to the pluralityof selectively controllable switches to apply a selected space-timecoding protocol on the plurality of antenna components.

The processing unit generates adaptive control signals to the pluralityof selectively controllable switches to selectively apply a selectedspace-time coding protocol, spatial multiplexing or a selected beamforming protocol together on the plurality of antenna componentsdepending on channel conditions.

The processing unit generates adaptive control signals to the pluralityof selectively controllable switches to apply a selectedradiation/polarization protocol on the plurality of antenna componentsaccording to transmission scheme or channel condition.

The processing unit generates adaptive control signals to the pluralityof selectively controllable switches to apply a selected optimizedradiation/polarization protocol on the plurality of antenna componentsaccording to transmission scheme and channel condition.

The processing unit generates adaptive control signals to the pluralityof selectively controllable switches to dynamically reconfigure thestructural geometry of the antenna.

The processing unit generates adaptive control signals to the pluralityof selectively controllable switches to alter the frequencycharacteristics of the antenna.

The processing unit generates adaptive control signals to the pluralityof selectively controllable switches to dynamically reconfigure theantenna radiation/polarization and frequency characteristics by alteringthe physical structure of the antenna.

The processing unit generates adaptive control signals to the pluralityof selectively controllable switches to dynamically alter the antenna tooptimally respond to changes in the propagation environment withchanging multipath conditions.

The improvement is used in combination with multiuser wireless networksincluding cellular mobile communication systems, wireless local areanetworks, mission-centric or individual-centric implementations ofwireless ad-hoc networks, or sensor networks.

The processing unit generates adaptive control signals to the pluralityof selectively controllable switches to selectively alter the arrayfactor and the element factor of the reconfigurable antenna.

The improvement further comprises a plurality of multifunctionreconfigurable antennas selectively arranged and configured into areconfigurable antenna array.

The processing unit generates adaptive control signals to the pluralityof selectively controllable switches to selectively interrelatetransmission algorithms, radiation/polarization characteristics of thereconfigurable antenna, configuration of the reconfigurable antenna, andpropagation environment to optimize communication performance at alltimes.

The processing unit generates adaptive control signals to the pluralityof selectively controllable switches to selectively determine the numberof antenna elements communicated to a corresponding transmissionalgorithm.

The processing unit generates adaptive control signals to the pluralityof selectively controllable switches to utilize available partialchannel information to dynamically change antenna behavior and providethe optimal performance in all cases to converge to space-time codingwhen the transmitter does not know the channel at all and to converge tobeam forming when the transmitter knows the channel perfectly.

The processing unit generates adaptive control signals to vary antennaelement separation with geometric reconfigurability in the antenna.

The processing unit generates adaptive control signals to alteroperating frequency for space-frequency coding in MIMO-orthogonalfrequency-division multiplexing (MIMO-OFDM).

The improvement further comprises a common substrate and the switchescomprise RF MEMS switches monolithically integrated on the commonsubstrate with the antenna. The common substrate comprises a microwavelaminate printed circuit board or at least comprises a printed circuitboard compatible with RF MEMS technology.

The switch comprises an RF-MEM actuator and where the antenna componentscomprise pixels patches in which two adjacent pixel patches areinterconnected by the RF-MEM actuator and are arranged a pixel-patchantenna array. The RF-MEM actuator comprises a conductive movablemembrane suspended over opposing and unconnected conductive stubsextending from adjacent pixel-patches in the array, so that when avoltage to applied between the membrane and the stub an electromagneticforce moves the suspended membrane into one of two electrical conductionstates with the stub to selectively connect or disconnect thepixel-patches.

The improvement further comprises a reconfigurable feed circuit coupledto the antenna which is selectively controllable to dynamically matchthe antenna impedance depending on the modes of operation of theantenna. The reconfigurable feed circuit comprises at least twoselectively controllable radial stubs and a selectively controllablequarter-wave transformer.

The processing unit is coupled to the reconfigurable feed circuit toconnect selected ones of the stubs and to selectively control theselectively connected radial stubs and quarter-wave transformer toachieve desired impedance matching for a targeted mode of operation.

The processing unit generates adaptive control signals according toreconfigurable modes of operation characterized by a selected one orones of a plurality of operating frequencies and characterized by aselected one or ones of a plurality of reconfigurable polarizations ofthe radiated field.

The implementation of reconfigurable modes of operation characterized bya selected one or ones of a plurality of operating frequencies isachieved by changing the architecture of the antenna.

The illustrated embodiment also includes an improvement in a method ofoperating an adaptive MIMO communications system according to any one ofthe foregoing descriptions.

In particular, the illustrated embodiment is an improvement in a methodof optimizing operation of an adaptive MIMO communications systemcomprising operating a plurality of multifunction reconfigurableantennas to introduce an additional degree of freedom by treating thephysical antenna array configuration and its radiation/polarization andfrequency properties as adaptive system parameters.

The illustrated embodiment is an improvement in a method of operating anadaptive MIMO communications system comprising operating a plurality ofmultifunction reconfigurable antennas according to a plurality ofadaptive coding schemes to optimally respond to the changes in thepropagation environment with rapidly changing multipath conditions inwhich reconfiguration of antenna properties and array configuration isdynamically combined with selection of the adaptive coding scheme toprovide an optimal communication. The step of operating a plurality ofmultifunction reconfigurable antennas comprises: jointly optimizingcommunication by beam forming, or space-time coding, spatialmultiplexing or any other transmission signaling scheme; or selectingthe properties and array configuration as additional components in ajoint optimization of the adaptive system by selecting parameters of theantenna properties and configuration in conjunction with an adaptedtransmission scheme with respect to the channel condition.

The step of selecting parameters of the antenna properties andconfiguration in conjunction with an adapted transmission scheme withrespect to the channel condition comprises changing antenna properties,such as radiation pattern, polarization, operating frequency, to shapethe characteristics of the propagation environment for the advantage ofthe transmission signaling schemes so that an optimal combination ofsystem parameters are dynamically selected.

While the apparatus and method has or will be described for the sake ofgrammatical fluidity with functional explanations, it is to be expresslyunderstood that the claims, unless expressly formulated under 35 USC112, are not to be construed as necessarily limited in any way by theconstruction of “means” or “steps” limitations, but are to be accordedthe full scope of the meaning and equivalents of the definition providedby the claims under the judicial doctrine of equivalents, and in thecase where the claims are expressly formulated under 35 USC 112 are tobe accorded full statutory equivalents under 35 USC 112. The inventioncan be better visualized by turning now to the following drawingswherein like components are referenced by like numerals.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a block diagram of conventional smart antenna array.

FIG. 1 b is a block diagram of a multifunctional reconfigurable antennaarray according to the invention.

FIG. 2 a is a schematic of a multifunctional reconfigurable pixel-patchantenna architecture using RF MEMS actuators.

FIG. 2 b is a top view of one of the RF MEMS actuators of FIG. 2 a.

FIG. 2 c is a side cross-sectional view one of the RF MEMS actuators ofFIG. 2 a shown in the down position.

FIG. 2 d is a side cross-sectional view one of the RF MEMS actuators ofFIG. 2 a shown in the up position.

FIG. 3 a is a schematic of a multifunctional reconfigurable pixel-patchantenna architecture arranged and configured for dual frequencyoperation at 4.1 GHz, mode₂₁ in Table I.

FIG. 3 b is a schematic of a reconfigurable pixel-patch antennaarchitecture arranged and configured for dual frequency operation at 6.4GHz, mode₁₁ in Table I.

FIG. 4 a is a schematic of a multifunctional reconfigurable pixel-patchantenna architecture arranged and configured for linear X polarization,mode₂₂ at 4.1 GHz in Table I.

FIG. 4 b is a schematic of a multifunctional reconfigurable pixel-patchantenna architecture arranged and configured for linear Y polarization,mode₂₃, at 4.1 GHz in Table I.

FIG. 5 a is a schematic of a multifunctional reconfigurable pixel-patchantenna architecture arranged and configured for right hand circularpolarization, mode₂₄, at 4.1 GHz.

FIG. 5 b is a schematic of a multifunctional reconfigurable pixel-patchantenna architecture arranged and configured for left hand circularpolarization, mode₂₅, at 4.1 GHz.

FIG. 6 a is a graph of the measured and calculated return losses as afunction of frequency for the antenna in mode₂₁ in Table I.

FIG. 6 b is a graph of the measured and calculated return losses as afunction of frequency for the antenna in mode₂₅ in Table I.

FIG. 6 c is a graph of the measured and calculated radiation patternsfor the antenna in x-z plane in mode₂₁ in Table I.

FIG. 6 d is a graph of the measured and calculated radiation patternsfor the antenna in x-z plane in mode₂₅ in Table I.

FIG. 7 is a diagram which illustrates how the multifunctionalreconfigurable antenna of the invention integrated with space-timecoding techniques to the propagation environment provides additionaldegree of freedom in adaptive optimization to close the gap betweentheoretical MIMO performance and practice.

The invention and its various embodiments can now be better understoodby turning to the following detailed description of the preferredembodiments which are presented as illustrated examples of the inventiondefined in the claims. It is expressly understood that the invention asdefined by the claims may be broader than the illustrated embodimentsdescribed below.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Multi-input multi-output (MIMO) systems with associated technologiessuch as smart antennas and adaptive coding and modulation techniquesenhance channel capacity, diversity, and robustness of wirelesscommunications as has been proven by many recent research results boththeoretically and experimentally. This disclosure focuses on the antennaaspect of MIMO systems 10. In particular, we disclose the important roleof the multifunctional reconfigurable antenna 12 and its links withspace-time coding techniques that can be employed for furtherexploitation of the theoretical performance of MIMO wireless systems 10.

The advantages of the multifunctional reconfigurable antenna 12 comparedto the conventional smart antenna are discussed below. Establishment ofmultifunctional reconfigurable antennas 12 requires novel radiofrequency microelectromechnical systems (RF MEMS) technology, which wehave developed. We disclose this technology with emphasis on itsdistinct advantages over existing silicon-based MEMS technologies formultifunctional reconfigurable antennas 12. A multifunctionalreconfigurable antenna design that can change its operating frequencyand radiation/polarization characteristics is disclosed. Finally, wepresent experimental and theoretical results from impedance andradiation performance characterization for different antennaconfigurations.

Turn now to the concept of a multifunctional reconfigurable antenna 12and its potential impact on MIMO systems 10. In the literature, a smart,intelligent, or adaptive antenna refers to an antenna array of elementsthat are typically standard monopoles, dipoles, or patches. The antennaelements themselves do not posses any intelligence. The intelligence isperformed in the signal-processing domain where the time domain signalsfrom or to the individual antenna elements are weighted and combined ina way that the resulting radiation pattern, i.e. the spatial response ofthe array, satisfies some type of determined conditions. This is the keyconcept of beam forming through which the electromagnetic energy isfocused in the direction of the desired signal while a null placed inthe direction of noise or interference sources.

On the other hand, a multifunctional reconfigurable antenna array 14 iscomprised of antenna elements 12 each of which has some intelligence.This intelligence stems from the ability of reconfiguring the physicalstructure of individual elements through which polarization/radiationand frequency properties of the array 14 are changed. The elements inthe multifunctional reconfigurable antenna array 14 have the ability tointelligently process the signals in spectral and angular domains addingto the already present time domain processing of the system 10. In thelanguage of phased-array antennas, a multifunctional reconfigurableantenna array 14 does not only alter the array factor but also theelement factor. In current phased-array technology, the element factorcannot be modified once individual elements are laid out.

FIGS. 1 a-1 b are block diagrams of a conventional smart antenna array16 and a multifunctional reconfigurable antenna array 14, respectively.Multifunctional reconfigurable antennas 12 having elements 18 include anintelligent control means 20 for altering the array factor and elementfactor. Antenna 12 is coupled to a summing circuit 22 whose output inturn is coupled to a processing unit 24, which feedback to antennas 12to provide for reconfiguration of array 14 and antennas 12 as describedbelow. Processing unit 24 may be a general purpose or special purposecomputer controlled by software or firmware, or may be a digital oranalog signal processing or logic circuit. The means by which suchcircuits can be designed, configured or programmed to perform thefunctions disclosed in this specification according to the invention areconventional.

In a multifunctional reconfigurable array 14, the antenna elementspacing can also be changed allowing efficient selection, application ofbeam forming and space-time coding schemes. While beam forming requiresantennas to be closely spaced (antennas are correlated) to avoid thenegative effects of side lobes, space-time coding will perform well ifthe spacing between antennas is large enough to ensure low correlation.As a result, a MIMO system 10 with reconfigurability in the geometricaldomain of antenna will not be constrained to use the same antenna designover varying channel conditions, which results in better utilization ofthe available channel capacity.

Finally, a multifunctional reconfigurable antenna 12 is alsoadvantageous in terms of antenna real estate. In today's miniature,compact, and highly integrated telecommunication devices the areadevoted to antenna elements 12 is typically very limited. This hasprompted antenna community to actively research small efficient antennadesign. However, the performances of an antenna (gain, bandwidth,efficiency) of a given electrical size are governed by laws ofelectromagnetism that dictate the fact that the smaller the size of anantenna the lower the performance. In other words, in designing a smallsize antenna there is always a compromise among size, bandwidth, andefficiency. Multifunctional reconfigurable antenna architecture, on theother hand, makes very efficient use of limited area by taking advantageof combined multiple functions in one single antenna 12. This results insignificant reduction in the area occupied by the multiple antennaelements 12 with enhanced functionality and performances.

Turn to consider links among transmission algorithms, radiation and/orpolarization characteristics and configuration of the antenna array 14,and the environment. Here, we identify relationships among thetransmission algorithms, the radiation/polarization characteristics andthe configuration of the multifunctional reconfigurable antenna 12, andthe propagation environment. These relationships enable the jointadjustment of the characteristics of the multifunctional reconfigurableantenna array 14 and the coding schemes over varying channel conditionsto optimize communication performance at all times.

Number of Antenna Components:

The most basic relationship, which does not require reconfigurability inthe geometrical domain of the multiple antennas 12, relates the numberof antenna elements 18 to a specific transmission algorithm. Formultiple antennas 12 if the number of transmit antennas 12 is largerthan two then it is not possible to design orthogonal space-time blockcodes (STBCs). Space-time block coding is a technique used in wirelesscommunications to transmit multiple copies of a data stream across anumber of antennas and to exploit the various received versions of thedata to improve the reliability of data-transfer. The fact thattransmitted data must traverse a potentially difficult environment withscattering, reflection, refraction and so on as well as be corrupted bythermal noise in the receiver means that some of the received copies ofthe data will “better” than others. This redundancy results in a higherchance of being able to use one or more of the received copies of thedata to correctly decode the received signal. In fact, space-time codingcombines all the copies of the received signal in an optimal way toextract as much information from each of them as possible. Space-timeblock codings as originally introduced, and as usually studied, areorthogonal. This means that the space-time block coding is designed suchthat the vectors representing any pair of columns taken from the codingmatrix are orthogonal. The result of this is simple, linear, optimaldecoding at the receiver. Its most serious disadvantage is that all butone of the codes that satisfy this criterion must sacrifice someproportion of their data rate. There are also space-time block codingdesigns that allows some inter-symbol interference, but can achieve ahigher data rate, and even a better error-rate performance, in harshconditions.

In case of more than two antennas 12, recently developedquasi-orthogonal space-time block codes have been used by others toachieve full rate and full diversity at the expense of slight increasein decoding complexity. For high signal-to-noise ratios (SNRs) and avery large number of antennas 12 spatial multiplexing is favorable overspace-time block codes, since data rate of spatial multiplexingincreases linearly with the increasing number of antennas 12 whilediversity gain of space time code blocks will saturate.

2. Array Configuration and Polarization:

Besides the number of antenna elements 18, the subset of the elementsselected in an array configuration is an important factor to achieve themajority of the capacity available in the channel. This does not onlyimprove performance but also results in a MIMO system 10 with lesscomplexity as the number of the transmit and receive RF chains arereduced. The performance can be further enhanced if the polarizations ofthe elements 18 are also taken into account as the propagation of theelectric field for different polarizations differs depending on theenvironment. It has been shown experimentally that for a line-of-sight(LOS) indoor environment vertically polarized systems achieve highercapacity than horizontally polarized ones. Moreover an antenna array 14with hybrid polarization, i.e. some elements are vertically polarizedwhile others are horizontally polarized, perform better than singlepolarization systems for both line-of-sight and non-line-of-sight (NLOS)conditions.

In practical communication scenarios degenerate channel phenomena calledthe “keyhole channel” effect may arise where the antenna elements 18both at the receiver and the transmitter have very low correlation dueto rich scattering, and yet the channel matrix has a very low rankresulting in a single mode of communication. This shows that lowcorrelation itself is not a guarantee for achieving high capacity. Ithas been shown in the art that in an outdoor propagation scenario thekeyhole problem may be avoided by using horizontally orientedtransmitter array instead of vertically oriented array. As aconsequence, both the array configuration and the polarization of eachindividual element 18 need to be adaptive in order to maintain thechannel performance over varying characteristics of the propagationenvironment.

A multifunctional reconfigurable antenna array 14 that can change itsconfiguration and polarization has the characteristics necessary toadapt variable transmission/receiving environments.

Spatial and Polarization Antenna Diversity:

A compromise between data rate maximization and diversity maximization,i.e. choosing between spatial multiplexing and space time codes, isimportant in realizing MIMO gains since the performance of thesesignaling strategies is strongly dependent on time-varying channelcharacteristics. As is known spatial multiplexing performs particularlywell in high SNR region, while space time code has better performance ina low SNR region. It has been shown in the art that while havingmultiple linear polarization diversity antennas at both ends of the linkdegrades the performance of space time code blocks in comparison tospatial diversity, significant improvements in the symbol error rate fora spatial multiplexing scheme are achieved in certain channel conditionssuch as in environments with high scattering density and with a highK-factor. The k-factor in ionospheric radio propagation is a correctionfactor that (a) is applied in calculations related to curved layers, and(b) is a function of distance and the real height of ionosphericreflection.

This leads to an important conclusion. A multifunctional reconfigurableantenna array 14 that can readily switch between polarization andspatial diversity schemes is needed to optimize an antenna performancefor a given coding scheme, i.e., spatial multiplexing or space time codeblocks, in a given channel environment.

4. Beam Forming, MIMO with Space Time Codes:

When only the receiver knows the channel, space-time codes achieve themaximum diversity in a system with multiple transmit antennas. On theother hand, if the transmitter knows the channel perfectly, beam formingis the optimal solution. In some practical cases, the transmitter hassome but not perfect information about the channel, for example the meanor variance. When side information is available at the transmitter thisinformation can be exploited to enhance the performance. Even when thechannel information is based on poor channel estimation, the use of thisinformation improves the performance of the system in combating fading.

The improvement can be achieved by combining space time codes and beamforming. Typically, when the quality of the channel feedback is high,the diversity rank is less critical and the transmitter should lay mostenergy on the “good” beam. On the other hand, when the feedback isunreliable, we should rely more on diversity and distribute energyevenly among different beams.

At the extreme case, when the channel feedback quality is so poor thatit is entirely independent of the actual situation, the system becomesan open-loop system and the beam forming scheme should gradually fallback to non-beam formed conventional space-time coding. Therefore, theperformance of the scheme should be similar to that of the originalspace-time code.

This requires the design of an adaptive system that can utilize theavailable partial channel information to change its behavior and providethe optimal performance in all cases. Such an adaptive system shouldconverge to space-time coding when the transmitter does not know thechannel at all and to beam forming when the transmitter knows thechannel perfectly.

Performance can be improved further if the optimal array design isemployed simultaneously. While antenna elements 18 are closely spacedand correlated in beam forming arrays, MIMO systems 10 employingspace-time coding require large antenna spacing for uncorrelatedantennas. It is also important to note that beam forming is moreeffective if the propagation environment has low scattering density,i.e., line of sight or near line of sight environment, resulting infewer multipaths. The weight selection algorithms can be more easilyoptimized for a few multipaths than for many. In contrast, space-timecodings take advantage of the multipath richness by maximizing data rateor diversity. The variation in antenna element separation would not bepossible without geometric reconfigurability in the antennas.

Although not discussed above, a multifunctional reconfigurable antenna12 can also change its operating frequency and may be useful forspace-frequency coding in MIMO-orthogonal frequency-divisionmultiplexing (MIMO-OFDM) systems.

Turn now and consider microwave laminate printed-circuit-boardcompatible RF MEMS technology. Before presenting the MEMS integratedmultifunctional reconfigurable antenna design we give a brief overviewof our MEMS technology, which offers some distinct advantages overexisting MEMS technologies in establishing such systems. RF MEMS havecreated significant impact due to their potential of revolutionizing RFand microwave system implementation for the next generation ofcommunication applications. In particular, RF MEMS switches have becomevery popular with their excellent switching characteristics, i.e., verylow insertion loss, very low power requirements, and high isolationwhich cannot be attained by semiconductor switches.

The breakthrough potential of RF MEMS, however, is offset by theshortcomings of the real-world features of RF-MEMS devices. A singlepackaged RF MEMS switch, despite its much better switching performance,suffers from impedance mismatch issues when deployed in a circuit due tothe distorting effects of the package interface. In addition thedevice-level packaging increases the cost per device, and its largeformat prohibits high densities of switches to be deployed in a singlesmall-form-factor circuit.

The key advantage of RF MEMS can be realized according to the inventionby system level implementation through monolithic integration capabilitywith other circuit components. This capability is key, in particular,for creating multifunctional and multifunctional reconfigurable antennasystems. Realization of monolithic integration requires a commonsubstrate for MEMS and antennas. However, microwave laminate printedcircuit boards (PCBs) with desired electrical characteristics forantenna applications cannot be used by existing silicon-based MEMStechnology owing to the process limitations imposed by printed circuitboards, such as low temperatures and non-planar surfaces. Highpermittivity materials such as Si and GaAs on which RF MEMS switches arecurrently fabricated are not a good choice for planar antennas due tothe deleterious effects of surface waves and unacceptable losses. Forthis reason, a MEMS integrated multifunctional reconfigurable antennafabricated by conventional technology cannot exploit monolithicintegration.

We have recently developed a RF MEMS technology compatible withmicrowave laminate printed circuit boards that overcomes the drawbacksof the silicon-based MEMS technology in establishing multifunctionalreconfigurable antennas with low cost and high performance. Thebreakthrough advantage of microwave laminate compatible RF MEMStechnology lies in making possible RF MEM switches on virtually anylaminates, plus monolithically integrating either single- or multi-layerantenna elements 18 with switches on this same substrate. Owing to themonolithic integration capability, MEMS becomes a physical part of theantenna 12, which is the key for a high degree of structuralreconfigurability. System level packaging then allows for reduced costand, by eliminating all wire bonds and most of the matching circuits,reduced loss, complexity, and size.

The details of printed circuit boards which are compatible with RF MEMStechnology and the associated fabrication processes are published andknown to those having ordinary skill in the art and are describedgenerally in B. A. Cetiner, et. al. “Monolithic Integration of RF MEMSSwitches With A Diversity Antenna on PCB Substrate” IEEE Trans.Microwave Theory and Tech., vol. 51, no. 1, pp. 332-335, January 2003;and H. P. Chang et. al. “Low Cost RF MEMS Switches Fabricated onMicrowave Laminate PCBs,” IEEE Electron Device Lett., vol. 24, no. 4,pp. 227-229, April 2003. Also see U.S. patent application Ser. No.10/751,131, which is incorporated herein by reference.

Consider a multifunctional reconfigurable pixel-patch antenna array,working mechanism, and its results. Here we focus on the design andcharacterization of a single multifunctional reconfigurable antennaelement 18 that can change its operating frequency and polarization. Itsarchitecture also allows one to vary element separation in an antennaarray 14. The radiation and impedance behaviors of the antenna 12 werecharacterized and compared to theory.

Architecture and Working Mechanism:

Shown in FIG. 2 a is the schematic of the proposed multifunctionalreconfigurable pixel-patch antenna architecture. It is built on a numberof printed rectangular shaped metallic pixels 18 interconnected by RFMEM actuators 26 on a microwave-laminated substrate 28. FIG. 2 b showsthe two adjacent pixels 18 interconnected by a RF-MEM actuator 26, whichis made of a conductive or metallic movable membrane 30, suspended overopposing and unconnected conductive or metal stubs 32 extending fromadjacent pixels 18 or strips of pixels 18, fixed to both ends throughmetallic posts 34. A DC bias voltage of approximately 50V appliedbetween the membrane 30 and the stub 32 causes an electrostatic forcethat moves or pulls the suspended membrane 30 on top of the stub 32 tothe actuator down state or actuator on, as diagrammatically depicted inFIG. 2 c which is a cross-sectional view of FIG. 2 a taken throughsection lines A-A′. The actuator 26 connects the pixels 18; otherwisepixels are disconnected (actuator up state or actuator off, as shown inthe same cross-sectional view of FIG. 2 d. Activation of theinterconnecting actuators 26, i.e. by keeping some of the actuators 26in the up position (zero bias) while activating the rest of them byapplying DC bias voltages, allows modifying the geometry and changingthe size through which multi-polarization and dual-frequency operationis achieved.

What has been illustrated is a normally open configuration whereapplication of the voltage closes a normally open connection throughmembrane 30 between two adjacent stubs 32. However, it must be clearlyunderstood that a normally closed configuration could be utilized withequal facility, where application of the voltage opens a normally closedconnection through membrane 30 between two adjacent stubs 32. Inaddition, connection or disconnection between more than two stubs 32could be employed if desired, such as might be used in non-raster arraysor in three-dimensional arrays in multilevel printed circuit boards formore complex array reconfigurations. Such extensions from theillustrated embodiment are expressly contemplated as being includedwithin the scope of the invention.

The antenna 12 is fed by a microstrip 36 or any transmission line alongits diagonal axis. This feed circuitry 38 is also multifunctionallyreconfigurable since the input impedance of radiating element changesdepending on the modes of operation, i.e. polarization states andoperating frequencies.

We use a transmission line or microstrip feed line 36 with radial stubs40 and quarter-wave transformer 42 as shown in FIG. 2 a. The electricallengths of the stubs 40 and transformer 42 are adjusted throughactivation/deactivation of MEM actuators 26 to achieve desired impedancematching for the targeted mode of operation. We also needed to use twostubs 40 since the stub location, in addition to its length, needs to bereconfigured depending on the operation scenario.

Multifunctional Reconfigurable Modes of Operation:

As shown in Table I, the antenna 12 of the illustrated embodimentprovides ten different multifunctional reconfigurable modes of operationcorresponding to the combination of two operating frequencies (4.1 GHzand 6.5 GHz) and five multifunctional reconfigurable polarizations ofthe radiated field (linear X, linear Y, dual linear, right handcircular, and left hand circular).

TABLE 1 Reconfigurable modes of operation Polarization Dual LinearLinear X Linear Y RHCP LHCP Frequency Upper Mode₁₁ Mode₁₂ Mode₁₃ Mode₁₄Mode₁₅ Frequency (6.4 GHz) Lower Mode₂₁ Mode₂₂ Mode₂₃ Mode₂₄ Mode₂₅Frequency (4.1 GHz)

Frequency reconfigurability is achieved by simply changing the size ofthe antenna 12. FIG. 3 a and FIG. 3 b show the schematics of dualfrequency band operation, mode₁₁ and mode₂₁. The upper frequency (6.4GHz) operation requires only 25 pixels to be connected as in FIG. 3 b,whereas for lower frequency (4.1 GHz) all 64 pixels are connected as inFIG. 3 a. Due to the diagonal feed circuitry, the antenna 12 radiatesdual linearly polarized waves since pixels are connected both in X- andY-direction as shown in FIGS. 3 a and 3 b.

Depending on the operating frequency the microstrip feed 36 is alsoreconfigured by adjusting the lengths of quarterwave transformer 42 andmatching stubs 40. Linear X- or linear Y-polarizations are obtained

by connecting the pixels either only in X-direction or only inY-direction, respectively.

FIG. 4 a and FIG. 4 b show the two cases, mode₂₂ and mode₂₃, withrequired reconfiguration made in feed circuitry for lower operatingfrequency. To obtain circular polarizations we use the antennageometries with internal slots 44 having proper dimensions and locationsfor a given operating frequency. Deactivation of specific MEM actuatorsintroduces these internal slots 44 into the pixel-patch antennageometry, which excites X and Y-polarized modes with equal amplitude and90-degree phase difference. Accordingly right and left hand circularlypolarized (RHCP and LHCP) radiation are achieved from each reconfiguredgeometry.

The schematics corresponding to each polarization scenario, mode₂₄ andmode₂₅ for lower resonant frequency are depicted in FIG. 5 a and FIG. 5b using selectively positioned holes 46. Operation modes correspondingto the higher resonant frequency are obtained in a similar manner andare not shown here, but can be readily determined by those havingordinary skill in the art based on the teachings of the invention. Notein each of the cases of FIGS. 3 a-5 b transformer 42 and stubs 40 arealso altered to provide appropriate tuning of the feed.

Performance Characterization

As described above, the multifunctional reconfigurable antennaarchitecture comprised of a large number of metallic pixels 18 andinterconnecting RF MEM actuators 26. It is clear that the fabrication ofthis complex structure is not feasible without employing monolithicintegration, which is also the case for silicon-based MEMS technology.The fabrication calls for printed circuit board compatible MEMStechnology described above.

In the illustrated embodiment we fabricated the simplified versions ofthe antenna geometry, where down state actuators were fabricated in thepermanent down state position (fabricated down) and up state actuatorswere modeled by an open circuit. The influence of this simplification onthe performance of the antenna 12 is negligible due to very lowinsertion loss and high isolation characteristics of RF MEMS actuators26 used in the antenna structure 12.

We selected two modes of operation, mode 21 and mode 25, as examples forperformance characterization. The antennas 12 were designed, fabricated,and tested. RO4003-FR4 (ε_(r)=3.38, tan δ=0.002) microwave laminate wasused as the substrate 28 due to its low cost and widespread use inwireless systems.

FIG. 6 a and FIG. 6 b show both theoretical and experimental results forthe return losses and the radiation patterns of the antenna in mode 21,dual linear polarization lower frequency. Theoretical analyses with afull wave simulation were performed using a finite element method (FEM)tool. Very good agreement between simulated and measured results wasobserved. The behavior of the antenna 12 is very similar to that ofconventional patch antenna with a bandwidth of 3% for a VSWR less thantwo.

Results for mode 25, right-hand circular polarization lower frequencyare given in FIG. 6 c and FIG. 6 d. As is seen from FIG. 6 d, thisantenna radiates a left hand circularly polarized wave normal to theplane of the antenna, in the +z-axis.

It may now be appreciated that wireless applications that areincreasingly bandwidth and mobility intensive have driven MIMO researchto push against the physical limits of coding and signaling. Themultifunctional reconfigurable antenna technology disclosed greatlyimpacts adaptive MIMO system design through the capability to change itsradiation and impedance characteristics. The multifunctionalreconfigurable antenna 12 integrated with space-time coding techniquesto the propagation environment provides additional degree of freedom inadaptive optimization, and thus the gap between theoretical MIMOperformance and practice is closed as symbolically illustrated by FIG.7. A novel RF MEMS process that enables very large-scale monolithicintegration of antenna and circuit components on common microwavelaminates 28 is described. A simplified prototype of the multifunctionalreconfigurable antenna is fabricated on a popular laminate and itsmultifunctional reconfigurable performances are found to be in goodagreement with our simulation.

The creation by the invention of a long awaited design space where theinterplay between multifunctional reconfigurable antennae 12 andadaptive coding can feed back to each other is likely to revolutionizebroadband MIMO system design methodology.

Many alterations and modifications may be made by those having ordinaryskill in the art without departing from the spirit and scope of theinvention. Therefore, it must be understood that the illustratedembodiment has been set forth only for the purposes of example and thatit should not be taken as limiting the invention as defined by thefollowing invention and its various embodiments.

Therefore, it must be understood that the illustrated embodiment hasbeen set forth only for the purposes of example and that it should notbe taken as limiting the invention as defined by the following claims.For example, notwithstanding the fact that the elements of a claim areset forth below in a certain combination, it must be expresslyunderstood that the invention includes other combinations of fewer, moreor different elements, which are disclosed in above even when notinitially claimed in such combinations. A teaching that two elements arecombined in a claimed combination is further to be understood as alsoallowing for a claimed combination in which the two elements are notcombined with each other, but may be used alone or combined in othercombinations. The excision of any disclosed element of the invention isexplicitly contemplated as within the scope of the invention.

The words used in this specification to describe the invention and itsvarious embodiments are to be understood not only in the sense of theircommonly defined meanings, but to include by special definition in thisspecification structure, material or acts beyond the scope of thecommonly defined meanings. Thus if an element can be understood in thecontext of this specification as including more than one meaning, thenits use in a claim must be understood as being generic to all possiblemeanings supported by the specification and by the word itself.

The definitions of the words or elements of the following claims are,therefore, defined in this specification to include not only thecombination of elements which are literally set forth, but allequivalent structure, material or acts for performing substantially thesame function in substantially the same way to obtain substantially thesame result. In this sense it is therefore contemplated that anequivalent substitution of two or more elements may be made for any oneof the elements in the claims below or that a single element may besubstituted for two or more elements in a claim. Although elements maybe described above as acting in certain combinations and even initiallyclaimed as such, it is to be expressly understood that one or moreelements from a claimed combination can in some cases be excised fromthe combination and that the claimed combination may be directed to asubcombination or variation of a subcombination.

Insubstantial changes from the claimed subject matter as viewed by aperson with ordinary skill in the art, now known or later devised, areexpressly contemplated as being equivalently within the scope of theclaims. Therefore, obvious substitutions now or later known to one withordinary skill in the art are defined to be within the scope of thedefined elements.

The claims are thus to be understood to include what is specificallyillustrated and described above, what is conceptionally equivalent, whatcan be obviously substituted and also what essentially incorporates theessential idea of the invention.

1. An improvement in an adaptive MIMO communications system comprising;a multifunctional reconfigurable antenna array with a selectivelyalterable effective physical antenna array configuration andradiation/polarization properties, which configuration and properties isa component in the optimization of the adaptive system parameters, and aprocessing unit coupled to the multifunctional reconfigurable antenna todetermine communication channel conditions for generating adaptivecontrol signals to the plurality of selectively controllable switches,wherein the antenna communicates through a channel between a transmitterand a receiver, and where the processing unit generates adaptive controlsignals to the plurality of selectively controllable switches to utilizeavailable partial channel information to dynamically change antennabehavior and provide the optimal performance in all cases to converge tospace-time coding when the transmitter does not know the channel at alland to converge to beam forming when the transmitter knows the channelperfectly.
 2. The improvement of claim 1 where the multifunctionalreconfigurable antenna comprises a plurality of antenna components and aplurality of selectively controllable switches coupling selected ones ofthe plurality of antenna components together into a multifunctionalreconfigurable subarray of antenna components.
 3. The improvement ofclaim 2 where the antenna components comprise monopoles, dipoles,patches or combinations thereof.
 4. The improvement of claim 2 furthercomprising a common substrate and where the switches comprise RF MEMSswitches monolithically integrated on the common substrate with theantenna.
 5. The improvement of claim 4 where the common substratecomprises a microwave laminate printed circuit board.
 6. The improvementof claim 4 where the common substrate comprises a printed circuit boardcompatible with RF MEMS technology.
 7. The improvement of claim 2 wherethe switch comprises an RF-MEM actuator and where the antenna componentscomprise pixel-patches of any geometric shape arranged in a pixel-patchantenna array in which two adjacent pixel patches are interconnected bythe RF-MEM actuator, and where the RF-MEM actuator comprises aconductive movable membrane suspended over opposing and unconnectedconductive stubs extending from adjacent pixel-patches in the array, sothat when a voltage to applied between the membrane and the stub anelectromagnetic force moves the suspended membrane into one of twoelectrical conduction states with the stub to selectively connect ordisconnect the pixel-patches.
 8. The improvement of claim 1 where theprocessing unit generates adaptive control signals to the plurality ofselectively controllable switches to apply a selected beam formingprotocol on the plurality of antenna components.
 9. The improvement ofclaim 1 where the processing unit generates adaptive control signals tothe plurality of selectively controllable switches to apply a selectedtransmission signaling scheme on the plurality of antenna components.10. The improvement of claim 1 where the processing unit generatesadaptive control signals to the plurality of selectively controllableswitches to selectively apply a spatial multiplexing, selectedspace-time coding protocol or a selected beam forming protocol on theplurality of antenna components depending on channel conditions.
 11. Theimprovement of claim 1 where the processing unit generates adaptivecontrol signals to the plurality of selectively controllable switches toapply a selected radiation/polarization protocol on the plurality ofantenna components according to transmission scheme or channelcondition.
 12. The improvement of claim 1 where the processing unitgenerates adaptive control signals to the plurality of selectivelycontrollable switches to apply a selected optimizedradiation/polarization protocol on the plurality of antenna componentsaccording to transmission scheme and channel condition.
 13. Theimprovement of claim 12 where the antenna is characterized by astructural geometry and where the processing unit generates adaptivecontrol signals to the plurality of selectively controllable switches todynamically reconfigure the structural geometry of the antenna.
 14. Theimprovement of claim 9 where the processing unit generates adaptivecontrol signals to the plurality of selectively controllable switches todynamically reconfigure the antenna radiation/polarization and frequencycharacteristics by altering the physical structure of the antenna. 15.The improvement of claim 1 where the antenna is characterized byfrequency characteristics and where the processing unit generatesadaptive control signals to the plurality of selectively controllableswitches to alter the frequency characteristics of the antenna.
 16. Theimprovement of claim 1 where the processing unit generates adaptivecontrol signals to the plurality of selectively controllable switches todynamically alter the antenna to optimally respond to changes in thepropagation environment with changing multipath conditions.
 17. Theimprovement of claim 1 where the multifunctional reconfigurable antennais characterized by an array factor and element factor and where theprocessing unit generates adaptive control signals to the plurality ofselectively controllable switches to selectively alter the array factorand the element factor of the multifunctional reconfigurable antenna.18. The improvement of claim 1 where the processing unit generatesadaptive control signals to the plurality of selectively controllableswitches to selectively interrelate transmission algorithms,radiation/polarization characteristics of the multifunctionalreconfigurable antenna, configuration of the multifunctionalreconfigurable antenna, and propagation environment to optimizecommunication performance at all times.
 19. The improvement of claim 1where the processing unit generates adaptive control signals to theplurality of selectively controllable switches to selectively determinethe number of antenna elements communicated to a correspondingtransmission algorithm.
 20. The improvement of claim 1 where theprocessing unit generates adaptive control signals to vary antennaelement separation with geometric reconfigurability in the antenna. 21.The improvement of claim 1 where the processing unit generates adaptivecontrol signals to alter operating frequency for space-frequency codingin MIMOorthogonal frequency-division multiplexing (MIMO-OFDM).
 22. Theimprovement of claim 1 where the processing unit generates adaptivecontrol signals according to multifunctional reconfigurable modes ofoperation characterized by a selected one or ones of a plurality ofoperating frequencies and characterized by a selected one or ones of aplurality of multifunctional reconfigurable polarizations of theradiated field.
 23. The improvement of claim 22 where the antenna ischaracterized by an alterable architecture, and where themultifunctional reconfigurable modes of operation characterized by aselected one or ones of a plurality of operating frequencies is achievedby changing the architecture of the antenna.
 24. The improvement ofclaim 1 in further combination with multiuser wireless networksincluding cellular mobile communication systems, wireless local areanetworks, mission-centric or individual-centric implementations ofwireless ad-hoc networks, or sensor networks.
 25. The improvement ofclaim 1 further comprising a plurality of multifunctional reconfigurableantennas selectively arranged and configured into a multifunctionalreconfigurable antenna array.
 26. The improvement of claim 1 furthercomprising a multifunctional reconfigurable feed circuit coupled to theantenna which is selectively controllable to dynamically match theantenna impedance depending on the modes of operation of the antenna.27. The improvement of claim 26 where the multifunctional reconfigurablefeed circuit comprises selectively controllable at least two radialstubs and a selectively controllable quarter-wave transformer.
 28. Theimprovement of claim 27 further comprising a processing unit coupled tothe multifunctional reconfigurable feed circuit to connect selected onesof the stubs and to selectively control the selectively connected radialstubs and quarter-wave transformer to achieve desired impedance matchingfor a targeted mode of operation.
 29. An improvement in a method ofoperating an adaptive MIMO communications system comprising: providing amultifunctional reconfigurable antenna, selectively reconfiguring themultifunctional reconfigurable antenna with a selectively alterableeffective physical antenna array and selectively alterableradiation/polarization properties to optimize adaptive systemparameters; and determining communication channel conditions, andgenerating adaptive control signals and communicating the controlsignals to the plurality of selectively controllable switches inresponse to the communication channel conditions, wherein the antennacommunicates through a channel between a transmitter and a receiver, andwhere generating adaptive control signals comprises applying adaptivecontrol signals to the plurality of selectively controllable switches toutilize available partial channel information to dynamically changeantenna behavior and provide the optimal performance in all cases toconverge to space-time coding when the transmitter does not know thechannel at all and to converge to beam forming when the transmitterknows the channel perfectly.
 30. The improvement of claim 29 where themultifunctional reconfigurable antenna comprises a plurality of antennacomponents and a plurality of selectively controllable switches, andwhere selectively reconfiguring the multifunctional reconfigurableantenna comprises coupling selected ones of the plurality of antennacomponents together into a multifunctional reconfigurable subarray ofantenna components.
 31. The improvement of claim 30 where couplingselected ones of the plurality of antenna components together into amultifunctional reconfigurable subarray of antenna components comprisesthe antenna components comprise selectively coupling together monopoles,dipoles, patches or combinations thereof.
 32. The improvement of claim30 further comprising providing a common substrate and monolithicallyintegrating the switches as RF MEMS switches on the common substratewith the antenna.
 33. The improvement of claim 32 where providing thecommon substrate comprises providing a microwave laminate printedcircuit board.
 34. The improvement of claim 32 where providing thecommon substrate comprises providing a printed circuit board compatiblewith RF MEMS technology.
 35. The improvement of claim 32 where theswitch comprises an RF-MEM actuator and where the antenna componentscomprise a pixel-patch antenna array and further comprisinginterconnecting two adjacent pixel patches by the RF-MEM actuator, andwhere the RF-MEM actuator, which comprises a conductive movable membranesuspended over opposing and unconnected conductive stubs extending fromadjacent pixel-patches in the array, by applying a voltage between themembrane and the stub so that an electromagnetic force moves thesuspended membrane into one of two electrical conduction states with thestub to selectively connect or disconnect the pixelpatches.
 36. Theimprovement of claim 29 where generating adaptive control signalscomprises generating and applying a selected beam forming protocol tothe plurality of antenna components.
 37. The improvement of claim 29where generating adaptive control signals comprises applying a selectedspace-time coding protocol to the plurality of antenna components. 38.The improvement of claim 29 where generating adaptive control signalscomprises selectively applying a selected space-time coding protocol ora selected beam forming protocol to the plurality of antenna components.39. The improvement of claim 29 generating adaptive control signalscomprises applying a selected radiation/polarization protocol to theplurality of antenna components according to transmission scheme orchannel condition.
 40. The improvement of claim 29 where generatingadaptive control signals comprises applying a selected optimizedradiation/polarization protocol to the plurality of antenna componentsaccording to transmission scheme and channel condition.
 41. Theimprovement of claim 40 where the antenna is characterized by astructural geometry and where generating adaptive control signalscomprises applying adaptive control signals to the plurality ofselectively controllable switches to dynamically reconfigure thestructural geometry of the antenna.
 42. The improvement of claim 41where generating adaptive control signals comprises applying adaptivecontrol signals to the plurality of selectively controllable switches todynamically reconfigure the antenna radiation/polarization and frequencycharacteristics by altering the physical structure of the antenna. 43.The improvement of claim 29 where the antenna is characterized byfrequency characteristics and where generating adaptive control signalscomprises applying adaptive control signals to the plurality ofselectively controllable switches to alter the frequency characteristicsof the antenna.
 44. The improvement of claim 29 where generatingadaptive control signals comprises applying adaptive control signals tothe plurality of selectively controllable switches to dynamically alterthe antenna to optimally respond to changes in the propagationenvironment with changing multipath conditions.
 45. The improvement ofclaim 29 where the multifunctional reconfigurable antenna ischaracterized by an array factor and element factor and where generatingadaptive control signals comprises applying adaptive control signals tothe plurality of selectively controllable switches to selectively alterthe array factor and the element factor of the multifunctionalreconfigurable antenna.
 46. The improvement of claim 29 where generatingadaptive control signals comprises applying adaptive control signals tothe plurality of selectively controllable switches to selectivelyinterrelate transmission algorithms, radiation/polarizationcharacteristics of the multifunctional reconfigurable antenna,configuration of the multifunctional reconfigurable antenna, andpropagation environment to optimize communication performance at alltimes.
 47. The improvement of claim 29 where generating adaptive controlsignals comprises applying adaptive control signals to the plurality ofselectively controllable switches to selectively determine the number ofantenna elements communicated to a corresponding transmission algorithm.48. The improvement of claim 29 where generating adaptive controlsignals comprises applying adaptive control signals to vary antennaelement separation with geometric reconfigurability in the antenna. 49.The improvement of claim 29 where generating adaptive control signalscomprises applying adaptive control signals to alter operating frequencyfor space-frequency coding in MIMO-orthogonal frequency-divisionmultiplexing (MIMO-OFDM).
 50. The improvement of claim 29 wheregenerating adaptive control signals comprises applying adaptive controlsignals according to multifunctional reconfigurable modes of operationcharacterized by a selected one or ones of a plurality of operatingfrequencies and characterized by a selected one or ones of a pluralityof multifunctional reconfigurable polarizations of the radiated field.51. The improvement of claim 50 where the antenna is characterized by analterable architecture, and where applying adaptive control signalsaccording to multifunctional reconfigurable modes of operation compriseschanging the architecture of the antenna.
 52. The improvement of claim29 where generating adaptive control signals comprises generatingadaptive control signals for use in multiuser wireless networksincluding cellular mobile communication systems, wireless local areanetworks, mission-centric or individual-centric implementations ofwireless ad-hoc networks, or sensor networks.
 53. The improvement ofclaim 29 further comprising selectively reconfiguring a plurality ofmultifunctional reconfigurable antennas into a multifunctionalreconfigurable antenna array.
 54. The improvement of claim 29 furthercomprising providing a multifunctional reconfigurable feed circuitcoupled to the antenna and selectively controlling the feed circuit todynamically match the antenna impedance depending on the modes ofoperation of the antenna.
 55. The improvement of claim 54 whereselectively controlling the multifunctional reconfigurable feed circuitcomprises selectively controlling at least two radial stubs and aquarter-wave transformer.
 56. The improvement of claim 55 wheregenerating adaptive control signals comprises connecting selected onesof the stubs and to selectively controlling the selectively connectedradial stubs and quarter-wave transformer to achieve desired impedancematching for a targeted mode of operation.